3.1. Description of the Variability in Agro-Morphological Parameters and Grain Quality Traits
The results of this study highlight significant agro-morphological variability and marked differences in quality traits among the studied durum wheat genotypes. agro-morphological parameters such as awn length (AWL), spike length (SL), number of spikelets per spike (SPS), number of grains per spike (GNS), thousand-grain weight (TGW), and grain yield (GY) exhibited significant variations, reflecting valuable genetic diversity. This diversity is accompanied by variations in key quality traits such as gluten content (GC), protein content (PC), dough strength (W), sedimentation capacity (SDS), and yellow index (YI), which are crucial for food product processing. Local landraces demonstrated exceptional performance, particularly in terms of spike length, thousand-grain weight, protein content, and gluten content. For instance, genotypes from these landraces showed a spike length (SL) of 8.78 cm, a thousand-grain weight (TGW) of 50.20 g, a protein content (PC) of 16.05%, and a gluten content (GC) of 36.89%. These traits are often associated with better adaptation to local environmental conditions, confirming the importance of these landraces as reservoirs of genetic diversity for breeding programs targeting arid regions.
Previous studies have demonstrated that landraces possess enhanced drought tolerance, enabling them to withstand water scarcity while maintaining stable yields even under adverse conditions. For example, wild wheat genotypes and landraces have shown strong drought avoidance and tolerance mechanisms, contributing positively to grain yield under drought stress [
39]. Moreover, landraces have been recognized as valuable sources of genetic diversity, with the potential to improve stress resilience and yield stability through modern breeding techniques, including genomic approaches that unlock their full genetic potential [
40]. This germplasm, composed of heterogeneous populations with high genetic diversity, exhibits remarkable adaptability to local environmental variations, particularly in the face of drought and heat stress, which are common in harsh environments. Wheat landraces have been cultivated for thousands of years under extreme conditions, and their genetic traits have been conserved, contributing significantly to their resilience in varying environments [
36]. Cultivated over many generations, local landraces have retained traits that enhance their resilience in unfavorable environmental conditions, making them well-suited to low-input agricultural systems. Unlike modern varieties, which prioritize genetic uniformity and high yields, landraces offer moderate but reliable yields while also contributing to biodiversity conservation and ecosystem sustainability [
41]. Among these traits, drought tolerance is particularly notable, as drought stress during grain filling can cause irreversible yield losses, underscoring the importance of tolerance mechanisms in maintaining productivity [
42] Furthermore, this type of germplasm plays a crucial role in breeding programs, offering a valuable foundation for developing cultivars better suited to extreme environments [
43,
44]. By harnessing this genetic wealth, it is possible to improve yields under rain-fed conditions while enhancing crop resilience in arid and semi-arid zones [
45]. These observations corroborate previous studies that emphasized the importance of wheat landraces in maintaining stable yields under environmental stress conditions. For instance, a study on Ethiopian durum wheat landraces revealed high genetic diversity among genotypes, with several showing high yields associated with phenotypic traits linked to grain quality and yield [
46]. Local wheat landraces, well adapted to low-input farming systems, exhibit greater resilience to challenging climatic conditions. While their yield is generally lower than that of modern varieties under optimal conditions, some landraces achieve comparable performance, particularly in organic farming. Their stability under rainfed conditions and adaptability to Mediterranean environments make them valuable candidates for sustainable production systems [
47,
48]. In addition to the agro-morphological and genetic characteristics of local landraces, key agronomic traits such as thousand-kernel weight (TKW) are critical for evaluating grain yield. However, genetic improvements have primarily enhanced yield through an increase in the number of grains, with TKW playing a secondary, yet important role in determining final yield [
49]. TKW is not only directly related to grain yield and milling quality but also influences seed vigor and growth, which in turn affect overall yield. Therefore, TKW serves as an essential indicator for assessing and optimizing wheat performance across diverse agricultural systems [
50].
Alongside TKW, spike length (SL) is another significant agronomic parameter influencing wheat yield. SL directly impacts grain density and the number of grains per spike, thereby contributing to higher overall productivity. Longer spikes are generally associated with a greater number of grains, which translates into increased grain yield. Moreover, SL plays a crucial role in adapting wheat to water deficit conditions, enhancing the plant’s resilience to environmental stresses and ensuring better grain adaptation under unfavorable conditions [
51]. Protein content is a pivotal determinant of durum wheat quality, particularly for pasta production, as it directly influences texture, elasticity, and cooking behavior. Durum wheat with a high protein content (≥13%, 11% dry matter) is preferred by pasta manufacturers due to its superior resistance to overcooking, optimal firmness, and reduced loss during cooking [
52]. Studies have shown that pasta made from semolina with a higher protein content exhibits enhanced strength and elasticity, making it superior to pasta made from lower protein content semolina [
53]. Additionally, Dexter and Matsuo [
54] observed that increased protein content improves cooking quality, particularly in Canadian durum wheat cultivars, enhancing overcooking tolerance and improving texture and stability post-cooking [
55]. Building on the importance of protein content, gluten, a key protein in wheat, plays a pivotal role in determining the suitability of flour for bread and pasta production. Wet gluten content serves as a critical indicator of dough behavior, influencing its elasticity and processability during baking. The quality and quantity of gluten, often measured by the gluten index, directly affect the texture and final quality of wheat-based products. Higher gluten content enhances dough’s viscoelastic properties, contributing to better product quality, including texture and stability, particularly in breadmaking [
56]. The gluten index, which varies among wheat varieties, quantifies both gluten quantity and its viscoelastic properties, and has been shown to be an important factor in determining the quality of biscuits and other baked goods [
57]. Furthermore, the viscoelastic properties of the dough, which are closely linked to grain protein levels, play a significant role in determining the quality of biscuits, particularly affecting texture and stability during baking [
58].
The Moroccan elite genotypes stand out for their promising performance, particularly regarding quality traits such as a high yellow pigmentation index. This trait is vital for the pasta industry, as the yellow-amber color of semolina has become a key quality factor for durum wheat end products [
59]. The yellow color is primarily due to carotenoid pigment content in the whole grain, commercially recognized as the yellow index (YI) in semolina [
60]. Beyond their aesthetic role, carotenoids provide significant nutritional benefits, offering antioxidant properties that contribute to human health. A high level of yellow pigments is sought after to ensure optimal color and quality in pasta, which in turn influences both its commercial and nutritional value [
61]. In addition to yellow pigments, the genetic diversity of durum wheat, particularly regarding glutenin alleles, plays a crucial role in determining gluten strength, which directly impacts pasta processing quality [
62]. These carotenoids, primarily lutein and its fatty acid esters, are responsible for the characteristic color of durum wheat. Their presence and concentration are key indicators of grain visual quality and suitability for industrial processing, especially for pasta production, where a bright yellow color is highly preferred [
63].
Remarkably, Moroccan varieties have demonstrated excellent performance in terms of yield, reaching up to 6.11 t/ha, even under prolonged water deficit conditions in the arid environment of Jemhâa Shaim. Compared to other germplasm types, these genotypes exhibited higher yields, confirming their resilience and ability to withstand water stress. Studies have shown that in arid regions like Jemhâa Shaim, durum wheat performance is strongly influenced by water scarcity and climate stress. In such conditions, selecting drought-tolerant genotypes is critical for ensuring stable production. Research by Daryanto et al.[
64] emphasizes the global impact of drought on wheat production, illustrating the importance of selecting varieties adapted to these extreme environmental stresses [
65]. Similarly, Aktaş [
66] highlighted the significance of drought tolerance indices in identifying landraces and genotypes that can withstand such stress, particularly for wheat production in water-limited areas like Jemhâa Shaim. Durum wheat yield is not only vital for ensuring food security but also plays a central role in supporting the local agricultural economy, especially in Mediterranean regions, where the crop demonstrates significant resistance to climatic challenges [
13]. In these environments, the ability of durum wheat genotypes to withstand climatic stresses directly influences their yield, making this crop a strategic asset for maintaining stable production, particularly in the face of climate change [
16]. This is supported by findings from a study on drought-tolerant durum wheat genotypes, which underscore the importance of selecting varieties that can thrive under both stressed and non-stressed conditions across varying climatic scenarios [
67]. Furthermore, in regions with arid climates, such as Jemhâa Shaim, selecting durum wheat genotypes adapted to these extreme environments is essential for ensuring stable production. These conclusions align with previous findings, which highlight that wheat genotypes capable of adapting to environmental stress conditions can offer higher yields and better performance, particularly in regions facing climatic challenges. In this context, Moroccan varieties have demonstrated strong adaptability to such conditions, further confirming their potential for future agricultural production and their role in ensuring stable yields under adverse environmental factors [
68].
3.2. Relationship Between Agronomic Traits and Yield Components
The results of this study reveal significant and intricate relationships among various agronomic traits of durum wheat, emphasizing the critical role of specific characteristics in enhancing productivity. A positive correlation was identified between spike length (SL) and the number of spikelets per spike (SPS), suggesting that longer spikes can support more spikelets, which improves grain distribution and contributes to overall yield. Additionally, spike length was shown to be a key determinant of grain yield. Similarly, a positive relationship has been demonstrated between spike length and both the number of spikelets per spike (SPS) and the number of grains per spike (GNS), emphasizing the importance of these traits in driving productivity, especially under optimal resource management [
69]. These findings align with the work of [
70] who reported that spike length is a vital trait influencing grain yield, further reinforcing its significance in maximizing productivity. A moderate negative correlation was observed between the number of grains per spike (GNS) and the thousand-grain weight (TGW), indicating that an increase in the number of grains may reduce the individual grain weight. This phenomenon reflects increased competition for essential resources, such as water and nutrients, particularly under limiting conditions [
71]. However, some studies have reported a positive correlation between these two parameters, which could be due to environmental factors or specific agricultural practices that favor both better grain development and optimal resource allocation for increased grain weight [
72]. Moreover, durum wheat’s behavior varies depending on environmental conditions. When sown in semi-arid areas, it adopts physiological strategies different from those observed under supplemental irrigation conditions, which may also influence the relationship between the number of grains per spike and their weight [
73].
The results of the correlation analysis between the different technological quality parameters of wheat revealed several interesting relationships. Notably, a strong correlation was observed between gluten strength and protein content, confirming previous studies that demonstrated protein content as a key factor in forming a high-quality gluten network. These findings are further supports by recent research [
26,
74], which highlighted a significant positive correlation between protein content and gluten content. These studies showed that high protein concentrations, particularly gluten, are essential for achieving an elastic and extensible dough, which are crucial characteristics for optimal breadmaking. From a technological perspective, a highly significant positive correlation was observed between protein content (PC), gluten content (GC), and bread-making strength (W). These results highlight the importance of high concentrations of protein, particularly gluten, in developing a gluten network that imparts optimal rheological properties to the dough, such as elasticity and extensibility, which are crucial for quality bread-making. These findings are consistent with the work, which demonstrated that PC is directly related to W, primarily through its role in gluten structure[
75]. Furthermore, the study highlighted that high molecular weight glutenin subunits contribute significantly to dough resistance and overall quality, further reinforcing their impact on W [
76,
77].
The results obtained in this study are consistent with those of previous research, such as studies on durum wheat genotypes, where it was observed that gluten strength is more influenced by the specific composition of gluten subunits, rather than simply by the total gluten or protein content [
78]. Although variations in gluten subunits have been correlated with dough strength, no direct link was found between the amount of gluten or proteins and gluten strength. These findings suggest that gluten strength may be more influenced by the structure and composition of the proteins, particularly the relative proportion of different fractions, rather than by their sheer quantity. This idea is further supported by the observations in the study of [
79], which indicate that gluten strength seems to result from a complex interaction between gluten subunits, rather than from the total protein content.
A highly significant positive correlation was observed between gluten strength (measured by the SDS test) and the yellow pigment index in the durum wheat genotypes analyzed. This relationship highlights the crucial influence of gluten quality on the final product’s color, particularly for pasta. These results align with those of the study conducted by Kaur et al.[
80], who also found a strong association between yellow pigment content and gluten quality in durum wheat varieties used for pasta production. Their study demonstrated that genotypes with higher yellow pigment content also exhibited better gluten quality, emphasizing the crucial role of protein composition in both the physical and visual quality of the final product. In addition,, the findings of the study by petter and shawry [
81] further support this correlation by demonstrating that variations in the composition of gluten subunits significantly influence dough properties as well as its color. They observed that the proportion of certain gluten fractions, such as glutenin and gliadin proteins, was closely linked to dough quality, including its color. Additionally, they highlighted that the composition of gluten proteins, particularly the relative proportion of different fractions, plays a crucial role in the quality of durum wheat-based products, especially pasta, where color is a key factor in visual quality [
82].